Closed-loop systems generally employ a feedback component that assesses the operation of the system and modifies aspects of the system based on the operational assessment. One example of such a system is a typical bar code scanner having an auto focus control system. Being closed-loop, the auto focus control system maintains or modifies the focus of optical components by analyzing images captured by the system. These systems often require long response times in refocusing a lens system, as many control and/or measurement cycles are performed during the image analysis in order to accurately determine the correct focus measurement.
Currently, bar code scanners and other machine-readable symbol imagers utilize a variety of lens actuator systems to provide auto focus control. These scanners often have problems related to the speed of correcting optical components (as described) and in the accuracy of measurement (e.g., open-loop scanners without feedback components). These and other problems exist with respect to providing auto focus control in bar code scanners.